In the case where carrier waves for IBOC type HD radio broadcasts are used, carrier waves for digital broadcasts can be added to carrier waves for analog broadcasts. Accordingly, it is possible in an HD radio receiver to increase sound quality using carrier waves for digital broadcasts. Carrier waves for digital broadcasts and carrier waves for such IBOC type HD radio broadcasts are arranged so as to be located on both sides adjacent to carrier waves for analog broadcasts in the frequency band (see, for example, JP-A-2000-4174 (FIG. 6, page 3)). These broadcast waves are referred to as hybrid type waves.
However, all broadcasting stations do not necessarily simultaneously send carrier waves for IBOC type HD radio broadcasts. Accordingly, in a case where carrier waves for digital broadcasts are added to both sides of carrier waves for analog broadcasts and sent, and a case where only carrier waves for analog broadcasts are sent, are possible. In the case where an HD radio receiver carries out a seeking (searching) operation in this situation, two types of spectra are mixed, and a problem arises in that the seeking operation stops by mistake and/or waves are improperly received.